The present invention relates to an installation for fluid production in a stretch of water, of the type comprising:                a top floating structure extending partly above the surface of the stretch of water;        a bottom structure fully submerged under the surface of the stretch of water, the bottom structure comprising a base positioned distant from the bed of the stretch of water, and means for anchoring the base onto the bed of the stretch of water;        at least one fluid conveying riser intended to connect a bed assembly positioned on the bed of the stretch of water to a surface assembly positioned on the top structure;        
the top structure being mobile between a production position mounted on the bottom structure, and an evacuation position placed away from the bottom structure, the installation comprising means for retaining the top structure in its production position.
Said installation is intended in particular for the conveying of hydrocarbons, recovered from the bed of a stretch of water, up to the surface through the stretch of water.
This type of installation generally comprises a floating structure, such as a platform arranged partly above the surface of the stretch of water, and a lower keel buoy anchored to the bed of the stretch of water. The top floating structure is reversibly fixed to the buoy.
The installation further comprises a plurality of flexible risers which connect a production assembly positioned on the bed of the stretch of water to an upper surface of the floating structure, via the buoy and the platform.
Said installation is intended for the production of hydrocarbon deposits for example, located in the bed of a stretch of water such as a lake, the sea or an ocean, under conditions in which the halting of production and rapidly performed safeguarding procedure of the production installation may be necessary.
Such conditions are encountered in particular in regions in which the stretch of water is temporarily or permanently covered with a layer of ice, as in polar regions.
In these regions, the layer of ice present on the surface of the stretch of water is relatively mobile. It may therefore partly damage the floating structure when it is anchored to the bed of the stretch of water.
Rapid safeguarding of the production installation may also be necessary when the atmospheric conditions on the surface of the stretch of water require fast evacuation of the platform.
This may be the case in particular in regions in which storms, even cyclones, are a possible occurrence.
To proceed with emergency disconnection, the flexible risers are first disconnected from the top floating structure.
Next, the means retaining the top floating structure on the bottom structure are released and the floating structure is convoyed from its production position towards an evacuation position in safer waters.
One example of an installation comprising a detachable floating structure is described in U.S. Pat. No. 7,197,999 to the Applicant. This installation is a platform of floating cylinder type known as a <<SPAR>> platform.
Said installation comprises a bottom structure having flexible securing cables secured onto the top structure, which can be swiftly and easily detached to allow evacuation of the top structure.
However, the subsequent re-connecting of the bottom structure to the top structure requires the re-connection of each cable onto the top structure, which can be tedious.